A regulatory variant impacting TBX1 expression contributes to basicranial morphology in Homo sapiens

Changes in gene regulatory elements play critical roles in human phenotypic divergence. However, identifying the base-pair changes responsible for the distinctive morphology of Homo sapiens remains challenging. Here, we report a noncoding single-nucleotide polymorphism (SNP), rs41298798, as a potential causal variant contributing to the morphology of the skull base and vertebral structures found in Homo sapiens. Screening for differentially regulated genes between Homo sapiens and extinct relatives revealed 13 candidate genes associated with basicranial development, with TBX1, implicated in DiGeorge syndrome, playing a pivotal role. Epigenetic markers and in silico analyses prioritized rs41298798 within a TBX1 intron for functional validation. CRISPR editing revealed that the 41-base-pair region surrounding rs41298798 modulates gene expression at 22q11.21. The derived allele of rs41298798 acts as an allele-specific enhancer mediated by E2F1, resulting in increased TBX1 expression levels compared to the ancestral allele. Tbx1-knockout mice exhibited skull base and vertebral abnormalities similar to those seen in DiGeorge syndrome. Phenotypic differences associated with TBX1 deficiency are observed between Homo sapiens and Neanderthals (Homo neanderthalensis). In conclusion, the regulatory divergence of TBX1 contributes to the formation of skull base and vertebral structures found in Homo sapiens.

Anatomical determinants of occipitocervical fusion in skull base chordoma resection: a systematic review of the literature with illustrative cases

OBJECTIVE

Skull base chordomas are rare, locally osseo-destructive lesions that present unique surgical challenges due to their involvement of critical neurovascular and bony structures at the craniovertebral junction (CVJ). Radical cytoreductive surgery improves survival but also carries significant morbidity, including the potential for occipitocervical (OC) destabilization requiring instrumented fusion. The published experience on OC fusion after CVJ chordoma resection is limited, and the anatomical predictors of OC instability in this context remain unclear.

METHODS

PubMed and Embase were systematically searched according to the PRISMA guidelines for studies describing skull base chordoma resection and OC fusion. The search strategy was predefined in the authors' PROSPERO protocol (CRD42024496158).

RESULTS

The systematic review identified 11 surgical case series describing 209 skull base chordoma patients and 116 (55.5%) who underwent OC instrumented fusion. Most patients underwent lateral approaches (n = 82) for chordoma resection, followed by midline (n = 48) and combined (n = 6) approaches. OC fusion was most often performed as a second-stage procedure (n = 53), followed by single-stage resection and fusion (n = 38). The degree of occipital condyle resection associated with OC fusion was described in 9 studies: total unilateral condylectomy reliably predicted OC fusion regardless of surgical approach. After lateral transcranial approaches, 4 studies cited at least 50%-70% unilateral condylectomy as necessitating OC fusion. After midline approaches-most frequently the endoscopic endonasal approach (EEA)-at least 75% unilateral condylectomy (or 50% bilateral condylectomy) led to OC fusion. Additionally, resection of the medial atlantoaxial joint elements (the C1 anterior arch and tip of the dens), usually via EEA, reliably necessitated OC fusion. Two illustrative cases are subsequently presented, further exemplifying how the extent of CVJ bony elements removed via EEA to achieve complete chordoma resection predicts the need for OC fusion.

CONCLUSIONS

Unilateral total condylectomy, 50% bilateral condylectomy, and resection of the medial atlantoaxial joint elements were the most frequently described independent predictors of OC fusion in skull base chordoma resection. Additionally, consistent with the occipital condyle harboring a significantly thicker joint capsule at its posterolateral aspect, an anterior midline approach seems to tolerate a greater degree of condylar resection (75%) than a lateral transcranial approach (50%-70%) prior to generating OC instability.

MRI Insights in Chiari Malformation Type 1 and Variations With Hydrosyringomyelia

Chiari malformation (CM) type 1 is a complex neurological disorder characterized by the displacement of the cerebellar tonsils into the upper spinal canal. Hydrosyringomyelia (HSM), which frequently coexists with this condition, presents diagnostic and treatment problems due to its broad spectrum of symptoms. There are various forms of CMs, with CM type 1 (CM1) being the most common type. Magnetic resonance imaging (MRI) is the best imaging technique to properly identify and diagnose CM1 and HSM. Important imaging findings include downward displacement of the cerebellar tonsils across the foramen magnum, the appearance of the syrinx in the spinal cord, and the alteration of the flow dynamics of the cerebrospinal fluid. This study was conducted at Datta Meghe Medical College, Nagpur, and Government Medical College & Super Speciality Hospital, Nagpur, India. It focuses on the diagnostic use of MRI in CM1 and its variations associated with HSM. Individuals who are asymptomatic may not need any treatment; however, those who are symptomatic or have HSM may require surgical decompression and restoration of the flow. We discuss the findings of MRI of six cases of CM1 and its variants with HSM and search for possible underlying causes. We conclude that magnetic resonance imaging is an imaging modality for the identification and evaluation of CM1 in cases of HSM.

[Minimally invasive surgical treatment of extramedullary tumors at the level of craniovertebral junction: experience of the Burdenko Neurosurgical Center]

OBJECTIVE

To describe own experience of treating patients with extramedullary tumors at the level of craniovertebral junction using minimally invasive surgical approaches.

MATERIAL AND METHODS

The study included 29 patients who underwent minimally invasive microsurgical resection of extramedullary tumors at the level of craniovertebral junction. We analyzed the main clinical and surgical parameters.

RESULTS

Gross total resection was achieved in most patients with high degree of safety. Two patients required redo surgery due to CSF leakage and soft tissue cyst. Mean length of hospital-stay was 7 days. VAS score of pain syndrome at discharge was 2 points and 0 points after 3 months. No significant differences in neurophysiological monitoring indicators were observed (p=0.76).

CONCLUSION

Minimally invasive posterior approaches to extramedullary tumors at the level of craniovertebral junction can significantly reduce surgical trauma with equal extent of resection.

Innovations in craniovertebral junction training: harnessing the power of mixed reality and head-mounted displays

OBJECTIVE

The objective of this study was to analyze the potential and convenience of using mixed reality as a teaching tool for craniovertebral junction (CVJ) anomaly pathoanatomy.

METHODS

CT and CT angiography images of 2 patients with CVJ anomalies were used to construct mixed reality models in the HoloMedicine application on the HoloLens 2 headset, resulting in four viewing stations. Twenty-two participants were randomly allocated into two groups, with each participant rotating through all stations for 90 seconds, each in a different order based on their group. At every station, objective questions evaluating the understanding of CVJ pathoanatomy were answered. At the end, subjective opinion on the user experience of mixed reality was provided using a 5-point Likert scale. The objective performance of the two viewing modes was compared, and a correlation between performance and participant experience was sought. Subjective feedback was compiled and correlated with experience.

RESULTS

In both groups, there was a significant improvement in median (interquartile range [IQR]) objective performance with mixed reality compared with DICOM: 1) group A: case 1, median 6 (IQR 6-7) versus 5 (IQR 3-6), p = 0.009; case 2, median 6 (IQR 6-7) versus 5 (IQR 3-6), p = 0.02; 2) group B: case 1, median 6 (IQR 5-7) versus 4 (IQR 2-5), p = 0.04; case 2, median 6 (IQR 6-7) versus 5 (IQR 3-7), p = 0.03. There was significantly higher improvement in less experienced participants in both groups for both cases: 1) group A: case 1, r = -0.8665, p = 0.0005; case 2, r = -0.8002, p = 0.03; 2) group B: case 1, r = -0.6977, p = 0.01; case 2, r = -0.7417, p = 0.009. Subjectively, mixed reality was easy to use, with less disorientation due to the visible background, and it was believed to be a useful teaching tool.

CONCLUSIONS

Mixed reality is an effective teaching tool for CVJ pathoanatomy, particularly for young neurosurgeons and trainees. The versatility of mixed reality and the intuitiveness of the user experience offer many potential applications, including training, intraoperative guidance, patient counseling, and individualized medicine; consequently, mixed reality has the potential to transform neurosurgery.

Os odontoideum: database analysis of 260 patients regarding etiology, associated abnormalities, and literature review

Introduction

Since the first description of os odontoideum in 1886, its origin has been debated. Numerous case series and reports show both a possible congenital origin and origin from the secondary to craniovertebral junction (CVJ) trauma. We conducted a detailed analysis of 260 surgically treated cases to document the initial symptoms, age groups, radiographic findings, and associated abnormalities, aiming to enhance the confirmation of the etiology. A literature search (1970-2022) was performed to correlate our findings.

Methods and materials

A total of 260 patients underwent surgical management of a referral database of 520 cases (1978-2022). All patients were examined by plain radiography and myelotomography as needed until 1984, and since then, CT and MRI have been employed. History of early childhood (aged below 6 years) CVJ trauma was investigated, including obtaining emergency department's initial radiographs from the referral and subsequent follow-up. Associated radiographic and systemic abnormalities were noted, and the atlas development was followed.

Results

The age of the patients ranged from 4 to 68 years, mostly between 10 and 20 years. There were 176 males and 86 females. Orthotopic os odontoideum was identified in 24 patients, and 236 patients had dystopic os odontoideum. Associated abnormalities were found in 94 of 260 patients, with 73 exhibiting syndromic abnormalities and 21 having Chiari I malformation. Two sets of twins had spondyloepiphyseal dysplasia. Of 260 patients, 156 experienced early childhood trauma /. Among these, 54 initially presented with normal radiographs but later demonstrated anterior atlas hypertrophy. In addition, a smaller posterior C1 arch was observed, leading to the development of os odontoideum. Two children had initial CVJ trauma as documented by MRI, with subsequent classical findings of os odontoideum and atlas changes. Syndromic patients had an earlier presentation. The literature reviewed confirms the multifactorial etiology.

Conclusions

The early presentation and associated abnormalities (such as Down syndrome, Klippel-Feil syndrome, Chiari I malformation, spondyloepiphyseal dysplasia, Morquio syndrome, and others) along with case reports documenting familial, hereditary, and twin presentations strongly support a congenital origin. Likewise, surgical complications are more prevalent in syndromic patients (40%) compared to 15% in other cases, as reported in the literature. The documentation of normal odontoid in early childhood trauma cases followed by the later development of os odontoideum provides evidence supporting trauma as an etiological factor. This process also involves vascular changes in both the atlas and the formation of os odontoideum. Associated abnormalities exhibit an earlier presentation and are only seen in cases with a non-traumatic origin.

C1-C2 coronal and sagittal joint angle based treatment algorithm for the need of transoral odointectomy in complex craniovertebral junction anomalies with Clinico-Radiological outcome analysis

OBJECTIVE

Craniovertebral junction (CVJ) pathology by virtue of its complexity is a surgical challenge in the realm of neurosurgery. We analyzed the need for transoral odointectomy in view of their C1-C2 joint coronal and sagittal angle of 58 patients with complex CVJ anomalies treated surgically. The clinical and radiological outcome of the patients was assessed and a treatment algorithm is proposed.

METHODS

A total of 58 cases were included in the Prospective study over the period of 2 years. Patients were evaluated clinically, investigated, and operated with reduction and rigid internal fixation with screws and rod. The clinical outcome was measured by Modified Japanese orthopedic association score(mJOA) and radiologically by conventional craniometrics indices. Paired 't' test used for statistical analysis.

RESULTS

Mean age of patients: 30 years, with mean, follow up: 20.5 months. 46(80%) patients were operated by posterior and 12(20%) by combined approach (anterior transoral with posterior). Occipitocervial fixation was done in 15(25.8%) cases and C1-C2 fixation in 43(74.2%) cases. As compared to patients with low coronal angle, the patient with coronal angle >65° needed anterior decompression (87.5%) and all (100%) had Occipitocervical fixation. Clinical outcome analysis showed significant improvement in mean mJOA score (preop 11.9 Vs postop 14.6) after surgery. All craniometrics indices were significantly improved after surgery. The overall complication rate was 10% with a mortality of 1.7%. 6 months follow up completed in all patients with a 100% fusion rate.

CONCLUSION

Occipitocervical fixation and anterior decompression is required in increased C1-C2 joint CA (>65°) for bony realignment and adequate decompression. Measurement of C1-C2 joint coronal and sagittal angle in complex CVJ anomalies will easily anticipate the surgeon regarding the need for anterior decompression inform of transoral odointectomy.

A Novel Craniocervical Junction Compression Severity Index-Based Grading System for Multidirectional Quantification of the Biomechanics at Foramen Magnum of Chiari Malformation Type I

Objective  This study aimed to establish a novel grading system, based on the craniovertebral junction compression severity index (CVJCSI) for multidirectional quantification at the foramen magnum plane for Chiari malformation type I (CMI). Methods  The CVJCSI grading system was established to stratify patients based on the ventral (modified clivoaxial angle < 138°), dorsal (tonsil herniation), and central (brainstem herniation) CVJ (craniovertebral junction) compression, the CVJCSI grading system was established to stratify patients. The optimal surgical method for each grade was recommended by intragroup comparisons regarding the efficacy of the three operations. Finally, according to the CVJCSI grading system, a prospective validation trial was performed and surgically treated for internal validation. Results  Based on the retrospective study ( n  = 310), the CVJCSI included six grades: I: syrinx alone without compression; II: dorsal compression; III: dorsal and central compression; IV: ventral compression; V: dorsal and ventral compression; and VI: ventral, dorsal, and central compression. Among all available variables, only the CVJCSI and surgical methods significantly affected the CCOS. The CCOS scores, overall and for each CVJCSI grade, increased in the prospective cohort ( n  = 42) compared with that in the retrospective analysis. Conclusions  The CVJCSI can be used to stratify CMI patients. The higher the CVJCSI grade, the more severe the CVJ compression and the worse posterior fossa deformity. Meanwhile, the CVJCSI was negatively correlated with the CCOS. The lower the CVJCSI grade, the better the response to surgery, and the less-invasive surgical procedures were warranted. Finally, the prospective cohort study validated the proposed CVJCSI-based surgical protocols.

Pathogenesis and Staging of Craniovertebral Tuberculosis: Radiographic Evaluation, Classification, and Natural History

STUDY DESIGN

Retrospective cohort.

OBJECTIVE

To radiographically evaluate Craniovertebral junction (CVJ) tuberculosis infection pathogenesis and to propose a modification to the Lifeso classification.

METHODS

A cohort of patients with radiologically or microbiologically identified CVJ tuberculosis treated at a single tertiary referral center in a TB endemic area was queried for characteristics about clinical presentation, treatment, and radiographic evidence of bone destruction and abscess formation were included. Disease was classified according to the Lifeso grading system and bony lesions were classified as either type 1 (preservation of underlying structure) or type 2 (damage of underlying structure).

RESULTS

52 patients were identified (mean age 28.5 ± 13.4yr, 48% male; 14% with a prior history of tuberculosis). All presented with neck pain at presentation, 29% with rotatory pain, and 37% with myelopathy. Comparison by Lifeso type showed Lifeso III lesions had longer symptom durations (P = .03) and more commonly had periarticular or predental abscess formation (P < .05), spinal cord compression (P < .01), and more commonly involved the C2 body and atlanto-dental joint. Underlying bony destruction was more common for lesions of the lateral atlantoaxial joints and atlanto-dental joints in Lifeso III cases than in either Lifeso I or II (all P < .05).

CONCLUSIONS

The radiologic findings of the present series suggest CVJ TB infection may originate in the periarticular fascia with subsequent invasion into the adjacent atlanto-dental and lateral atlantoaxial joints in later disease. To reflect this proposed etiology, we present a modified Lifeso classification to describe the radiologic pathogenesis of CVJ TB.

Endoscopic Endonasal Approach to the Craniovertebral Junction Lesions: A Case Series of 18 Patients

Introduction  Odontoid pathologies constitute a special category because they may lead to instability. Instability is defined by abnormal spinal alignment under physiologic conditions (loads) such as standing, walking, bending, or lifting. Since instability poses a risk of cord damage, surgical interventions may be required for durable long-term stabilization. This study demonstrates operative technique and results of endoscopic endonasal approach to the odontoid pathologies. Methods  We conducted a retrospective study involving 18 patients who underwent endoscopic endonasal odontoidectomy (EEO) due to craniovertebral pathologies. Demographic data, clinical features of the patients, risk factors, and intraoperative and postoperative complications were reported in this series. Results  Satisfactory outcomes achieved in 16 patients based on comparing the modified Rankin scale before and after the surgery ( p  = 0.0001). The mean duration for EEO was 232.6 ± 18.8 minutes. The mean blood loss during surgery was 386.67 ± 153.04 mL. The mean duration of hospital stay was 7 days. All patients were extubated within a few hours after surgery. Despite of successful anterior decompression in the aforementioned cases, intraoperative cerebrospinal fluid (CSF) leakage, postoperative meningitis, and pulmonary thromboembolism occurred as complications. However, two intraoperative CSF leakages were managed by direct dural repair and fat graft; two patients died due to postoperative meningitis and pulmonary thromboembolism at 7 and 4 days after the second surgery. Conclusion  In conclusion, EEO can be effectively used for anterior decompression of the odontoid pathologies, despite the risk of complications.

Transtubular Transoral Approach for Irreducible Ventral Craniovertebral Junction Compressive Pathologies: Surgical Technique and Outcome

Introduction

To investigate the use of a tubular retractor to provide access to the craniovertebral junction (CVJ) sparing the soft palate with the aim of reducing complications associated with traditional transoral approach but yet allowing adequate decompression of the CVJ.

Materials and methods

Twelve consecutive patients with severe myelopathy (JOA-score less than 11) from ventral CVJ compression were operated between 2014-2020 using a tubular retractor assisted transoral decompression.

Results

All patients improved neurologically statistically (p=0.02). There were no posterior pharynx wound infections or rhinolalia. There was one case with incomplete removal of the lateral wall of odontoid and one incidental durotomy.

Conclusions

A Tubular retractor provides adequate access for decompression of the ventral compression of CVJ. As the tubular retractor pushed away the uvula, soft palate and pillars of the tonsils as it docked on the posterior pharyngeal wall, the traditional complications associated with traditional transoral procedures is completely avoided.

Incidental craniovertebral junction schwannoma: Surgical or radiosurgical management?

Craniovertebral junction (CVJ) schwannomas are rare tumors, showing direct involvement of the atlanto-occipital and atlanto-axial joints. Microsurgical removal is the standard of care to improve symptoms and local control, but stereotactic radiosurgery (SRS) is an option. Both, surgery, and SRS, may show risks of severe complications. A 41-year-old male was referred to our department after incidental finding of a right-sided C1 tumor. A CT angiogram with 3D reconstructions showed the close relationship between the tumor and the right vertebral artery (VA). A post-contrast enhancement MRI revealed the presence of an extradural mass, sited at the level of the CVJ, mainly at the level of the right articular mass of C1. After multidisciplinary assessment, involving the gamma-knife and neurosurgical teams, we performed a microsurgical resection of the tumor. Histology confirmed the diagnosis of schwannoma. At 1 year follow-up the patient is stable, with no recurrence of the tumor. CVJ schwannoma's current standard of care is surgical resection, but longitudinal studies are required, and should promoted promptly since the recent introduction of the new version of GKSRS that allow the treatment of CVJ's lesions.

Exploring the Pathogenesis of Atlanto-Occipital Instability in Chiari Malformation With Type II Basilar Invagination: A Systematic Morphological Study

BACKGROUND

Our previous study suggested that atlanto-occipital instability (AOI) is common in patients with type II basilar invagination (II-BI).

OBJECTIVE

To further understand the pathogenesis of AOI in Chiari malformations (CM) and CM + II-BI through systematic measurements of the bone structure surrounding the craniocervical junction.

METHODS

Computed tomography data from 185 adults (80 controls, 63 CM, and 42 CM + II-BI) were collected, and geometric models were established for parameter measurement. Canonical correlation analysis was used to evaluate the morphological and positional relationships of the atlanto-occipital joint (AOJ).

RESULTS

Among the 3 groups, the length and height of the condyle and superior portion of the lateral masses of the atlas (C1-LM) were smallest in CM + II-BI cases; the AOJ had the shallowest depth and the lowest curvature in the same group. AOJs were divided into 3 morphological types: type I, the typical ball-and-socket joint, mainly in the control group (100%); type II, the shallower joint, mainly in the CM group (92.9%); and type III, the abnormal flat-tilt joint, mainly in the CM + II-BI group (89.3%). Kinematic computed tomography revealed AOI in all III-AOJs (100%) and some II-AOJs (1.5%) but not in type I-AOJs (0%). Morphological parameters of the superior portion of C1-LM positively correlated with those of C0 and the clivus and significantly correlated with AOI.

CONCLUSION

Dysplasia of the condyle and superior portion of C1-LM exists in both CM and II-BI cases yet is more obvious in type II-BI. Unstable movement caused by AOJ deformation is another pathogenic factor in patients with CM + II-BI.

Endoscopic endonasal resection of craniovertebral junction osteomyelitis: illustrative cases

BACKGROUND

Operative management of craniovertebral junction (CVJ) osteomyelitis has traditionally been extracranial and focused on debriding the infection. In select patients, the endoscopic endonasal approach (EEA) with a focus on additional resection versus debridement may be preferred. The goal of this study is to present the authors' experience with the EEA with gross or subtotal resection for the treatment of osteomyelitis at the CVJ and describe their technique in the context of the literature.

OBSERVATIONS

Two patients of the authors' and 6 detailed case reports in the literature were identified with a mean age of 58.9 years. Most patients (n = 5; 62.5%) underwent skull base surgery and debridement (n = 5; 62.5%). Although more common, debridement was inferior to resection in terms of neurological improvement (66.7% vs. 100.0%) postoperatively. The majority (n = 7; 87.5%) of patients underwent occipitocervical fusion.

LESSONS

Osteomyelitis is an exceedingly rare lesion of the CVJ. Despite the region's delicate biomechanical stability, resection of infected bone may be superior to debridement alone in terms of clinical outcome. Given how well established the safety of the EEA is to this region, further study of outcomes with resection is warranted.

[Surgical and combined treatment of patients with craniovertebral junction meningioma: a single-center retrospective study of 196 cases]

Treatment of craniovertebral junction meningioma is a difficult task. Surgical treatment is the gold standard for these patients. However, it is associated with high risk of neurological impairment, while combined treatment (surgery + radiotherapy) provides more favorable outcomes.

OBJECTIVE

To present the results of surgical and combined treatment of patients with craniovertebral junction meningioma.

MATERIAL AND METHODS

There were 196 patients with craniovertebral junction meningioma who underwent surgical or combined (surgery + radiotherapy) treatment at the Burdenko Neurosurgery Center between January 2005 and June 2022. The sample included 151 women and 45 men (3.4:1). Resection of tumor was performed in 97.4% of patients, craniovertebral junction decompression with dural defect closure - 2%, ventriculoperitoneostomy - 0.5%. As the second stage, 40 patients (20.4%) underwent radiotherapy.

RESULTS

Total resection was achieved in 106 patients (55.2%), subtotal - 63 (32.8%), partial - 20 (10.4%), tumor biopsy was performed in 3 (1.6%) cases. Intraoperative complications occurred in 8 patients (4%), postoperative complications - in 19 (9.7%) cases. Radiosurgery was carried out in 6 (15%) patients, hypofractionated irradiation - 15 (37.5%), standard fractionation - 19 (47.5%) patients. Tumor growth control after combined treatment made up 84%.

CONCLUSION

Clinical outcomes in patients with craniovertebral junction meningioma depend on tumor dimensions, topographic and anatomical localization of tumor, resection quality and relationship with surrounding structures. Combined treatment of anterior and anterolateral meningiomas of the craniovertebral junction is preferable compared to total resection.

Surgical, Clinical, and Radiological Outcomes Analysis of Craniovertebral Junction Anomalies Cases: An Institutional Experience

Objective  The aim of this study was to evaluate the clinical and radiological outcomes analysis of craniovertebral junction (CVJ) anomalies cases. Materials and Methods  Retrospective analysis of 43 CVJ anomalies cases, which were surgically managed at Uttar Pradesh University of Medical Sciences, Saifai, Etawah, Uttar Pradesh, India, from period between June 2015 and June 2019. They were analyzed for age, sex, clinical characteristics, radiological diagnosis, and treatment given. Patient's clinical and radiological status was assessed pre- and postoperatively during time of discharge and at 6 months of follow-up. For clinical assessment we used visual analogue scale (VAS) and Nurick grading system. Radiological assessment was done by atlantodental interval (ADI), craniobasal angle, and craniometric lines. Overall outcomes were depicted as favorable, stabilized, and mortality at 6 to 18 months (mean 12.69 ± 3.77) of follow-up. Results  The age range of our cases was 7 to 71 years (mean 29.93 ± 17.39). Male-to-female ratio was 2.91:1. Majority of the cases were presented with neck pain ( n  = 38; 88.37%), motor weakness ( n  = 35; 81.40%), and sensory deficits ( n  = 25; 58.14%). Congenital atlantoaxial dislocation ( n  = 31; 72.09) was the most common CVJ anomaly. Clinically, there were significant improvements in VAS ( p  = 0.001) and Nurick grade ( p  = 0.007) postoperatively. Radiologically, ADI ( p  = 0.003) had decreased, clivus canal angle ( p  = 0.005) become less acute, and odontoid process ( p  = 0.003 for McRae's line) goes downwards in postoperative period. Bony fusion was achieved in 41 (95.35%) cases. Out of 43, 73% cases had favorable outcomes, 21% were stabilized, and mortality was seen in 2.33% cases at 6 months (mean ± standard deviation = 12.69 ± 3.77) of follow-up. Conclusion  Proper preoperative evaluation and selection of individualized surgical technique was the key for excellent clinical and radiological outcomes with minimal complications.

Spinal manifestations of Ehlers-Danlos syndrome: a scoping review

OBJECTIVE

Since its initial description, the definition of Ehlers-Danlos syndrome (EDS) has notably changed. At present, it broadly refers to disorders of the connective tissue that are heritable and have similar features including joint hypermobility, dermal dysplasia, and vascular as well as internal organ fragility. There has been no comprehensive review of spinal manifestations of EDS in the recent literature. That has led to controversies in management protocols of this so-called orphan disease.

METHODS

The authors used the latest version of the EDS classification from 2017, in which 13 subtypes were recognized. EDS has 19 different causal genes, mainly associated with collagen synthesis. Of these, 5 subtypes have associated spinal manifestations.

RESULTS

Some of the spinal pathologies associated with EDS include Chiari malformation, craniocervical instability, kyphoscoliosis, segmental instability and kyphosis, spontaneous CSF leaks, Tarlov cyst syndrome, tethered cord, and problems associated with wound healing. Here, the authors briefly discuss the demographics, etiology, pathophysiology, clinical features, management strategies, and directions for further research for each of these manifestations.

CONCLUSIONS

EDS belongs to the group of orphan diseases, with the total patient population being below 200,000. Further research on spinal manifestations of EDS is the need of the hour to establish clinical practice guidelines and close the significant knowledge gaps that currently exist.

Angulation Between the Occipital Condyle and the Hypoglossal Canal: An Anatomical Study With Application in Transcondylar Approaches and Occipital Condyle Screw Placement

Background A detailed understanding of the relationship between the occipital condyle (OC) and the deeper-lying hypoglossal canal (HC) is necessary for surgeons who place screws into the OC or drill through or around the HC. Therefore, this anatomical study was performed. Methodology A total of 30 skulls (60 sides) underwent an analysis of the angle formed between the long axis of the OC and the HC, i.e., the OC/HC angle. Additionally, the lengths and widths of the OCs and foramen magnum (FM) of each skull were measured using a micrometer. Statistical analyses were performed between the left and right sides, and a Pearson's correlation coefficient was calculated between OC/HC angles and the sizes of the OCs and FM of the skulls. Results The OC/HC angle for the left and right sides ranged from 30 to 56 degrees (mean 46 degrees). The width of the OCs ranged from 9 to 18 mm (mean 13 mm). The length of the OCs was 18 to 31 mm (mean 24 mm). The mean length and width of the FM were 36 mm and 30 mm, respectively. There was no statistically significant difference between the OC/HC angle comparing left and right sides or male or female specimens. Additionally, no statistically significant differences were found between septated and non-septated HC. Pearson's correlation coefficient for left and right OC/HC angles and left and right OC lengths was r = 0.4056 and r = 0.2378, respectively. Pearson's correlation coefficient for left and right OC/HC angles and left and right OC width was r = 0.3035 and r = 0.3530, respectively. Pearson's correlation coefficient for left and right OC/HC angles and the width of the FM was r = 0.2178 and r = 0.2048, respectively. Pearson's correlation coefficient for left and right OC/HC angles and the length of the FM was r = 0.3319 and r = 0.2683, respectively. Conclusions The OC/HC angle as measured here was relatively consistent with no statistically significant differences between sides. We did not find a strong correlation between the width or length of the OC or the width or length of the FM and the OC/HC angles. Therefore, based on our study, surgeons can expect that this angle will range between 30 and 56 degrees (mean 46 degrees). Such knowledge might decrease patient morbidity following invasive procedures involving the OC.

Endoscopy-assisted high anterior cervical approach in craniovertebral junction (CVJ)

BACKGROUND

Surgical procedures in the craniovertebral junction (CVJ) suffer from specific challenges due to the proximity between the cranium and spine containing the critical neurovascular structures and the brainstem, respectively. Owing to the complex transitional zone, it is highly challenging for classic surgical approaches to practically acquire the additional exposure to neurovascular structures of the CVJ. Inspired by these facts, we explore the feasibility of an endoscopy-assisted high anterior cervical approach in the CVJ.

METHODS

To explore the feasibility of an endoscopy-assisted approach, we quantitatively assessed the surgical corridor and extent of exposure of the CVJ in 6 cadaveric specimens using 0° and 30° endoscopes.

RESULTS

The applied endoscopes provided adequate exposure to neurovascular structures and the brainstem in the CVJ. Notably, the resection of the anterior arch of C1 is avoided in minimal anterior clivectomy. Further, improved exposure of the CVJ is obtained after removing the odontoid.

CONCLUSION

An endoscope-assisted high anterior cervical approach in the CVJ significantly preserved the cervical spine stability while minimalizing the risk of neurovascular injury within the surgical corridor.

Rheumatoid Arthritis in Spine Surgery: A Systematic Review and Meta-Analysis

STUDY DESIGN

Systematic Review and Meta-analysis.

OBJECTIVE

The purpose of this study is to synthesize recommendations for perioperative medical management of RA patients and quantify outcomes after spine surgery when compared to patients without RA.

METHODS

A search of available literature on patients with RA and spine surgery was performed. Studies were included if they provided a direct comparison of outcomes between patients undergoing spine surgery with or without RA diagnosis. Meta-analysis was performed on operative time, estimated blood loss, hospital length of stay, overall complications, implant-related complications, reoperation, infection, pseudarthrosis, and adjacent segment disease.

RESULTS

Included in the analysis were 9 studies with 703 patients with RA undergoing spine surgery and 2569 patients without RA. In RA patients compared to non-RA patients undergoing spine surgery, the relative risk of infection was 2.29 times higher (P = .036), overall complications 1.61 times higher (P < .0001), implant-related complications 3.93 times higher (P = .009), and risk of reoperation 2.45 times higher (P < .0001). Hospital length of stay was 4.6 days longer in RA patients (P < .0001).

CONCLUSIONS

Treatment of spinal pathology in patients with RA carries an increased risk of infection and implant-related complications. Spine-specific guidelines for perioperative management of antirheumatic medication deserve further exploration. All RA patients should be perioperatively co-managed by a rheumatologist. This review helps identify risk profiles in RA specific to spine surgery and may guide future studies seeking to medically optimize RA patients perioperatively.

Measuring the shape and dimensions of normal the bony structures in the craniovertebral junction from computed tomography images of the pediatric age group

BACKGROUND

The aim of this study is to contribute to the literature by determining the morphometric reference values of the bony structures in the craniovertebral junction (CVJ) from computer tomography (CT) images of the pediatric age group.

METHODS

In this study, CT's of 151 simple trauma patients aged between 3 and 15 years between 2016 and 2020 were evaluated. All CT examinations were performed using a 32-slice CT and included images of the skull base and C1-C2 junction. A total of 10 measurements were obtained from these images, including Wachenheim clivus canal angle (WCA), Welcher basal angle (WBA), Cran-iocervical tilt angle (CCT), power ratio (PR), Atlantodens interval, McRae Line (MRL), McRae - Dens distance, basion-dens interval (BDI), basion-axis interval (BAI), and atlantooccipital measurement (AOM).

RESULTS

In comparison between gender groups, MRL (p=0.011) and AOM (p<0.001) measurements were found to be significantly higher in males. McRae-Dens distance, BDI, and AOM were significantly higher in patients aged 3-9 years (respectively, p=0005, p=0.003, p<0.001), and BAI (p=0.001) was significantly higher in patients aged 10-15 years. The McRae - Dens distance (p=0.119) was similar between patients with and without terminal ossicle in odontoid apex. But BDI of patients without terminal ossicle was significantly higher (p=0.048). All parameters, except the WCA, WBA, CCT, and PR, were statistically significantly correlated with the patient age (respectively, p=0.21, p=0.13, p=0.70, p=0.99).

CONCLUSION

In this study, the morphometric reference values of the bone structures at the CVJ were determined from the CT images of the pediatric age group.

Primary Meningeal Melanocytoma Located in the Craniovertebral Junction: A Case Report and Literature Review

Primary meningeal melanocytoma is a rare benign tumor in the central nervous system (CNS), comprising less than 0.1% of all intracranial tumors. A 44-year-old man presented with occipital headache, nausea, and vomiting. Computed tomography (CT) and magnetic resonance imaging (MRI) showed a well-defined intradural extramedullary mass lesion at the craniovertebral junction (CVJ). Gross total removal was achieved, and the patient improved symptomatically. The pathologic findings were consistent with meningeal melanocytoma. No tumor recurrence was seen on follow-up MRI two years after surgery. Cases of primary meningeal melanocytoma located at the CVJ are rare. The preoperative differential diagnosis of meningeal melanocytoma from meningioma is sometimes difficult because of their similar appearance on CT and MRI. Complete surgical removal is curative for most cases. We present a case of gross total removal of a meningeal melanocytoma located in the CVJ with references to the literature.

[Benign extramedullary spinal cord tumors at the level of craniovertebral junction: a systematic review]

Extramedullary spinal cord tumors at the level of craniovertebral junction are a rare group of neoplasms with their own characteristics. Taking into account the peculiarities of clinical course and complex anatomy of craniovertebral complex, these tumors present a complex diagnostic and surgical problem. A systematic review of literature data on epidemiology, clinical picture, diagnostic methods and dorsal minimally invasive methods of surgical treatment of patients with extramedullary spinal cord tumors of craniovertebral junction was performed.

Role of Three-dimensional Printing in Neurosurgery: An Institutional Experience

Background:

Recent advancements in three-dimensional (3D) printing technology in the field of neurosurgery have given a newer modality of management for patients. In this article, we intend to share our institutional experience regarding the use of 3D printing in three modalities, namely, cranioplasty using customized 3D-printed molds of polymethylmethacrylate, 3D-printed model-assisted management of craniovertebral (CV) junction abnormalities, and 3D model-assisted management of brain tumors.

Materials and Methods:

A total of 55 patients were included in our study between March 2017 and December 2019 at S. M. S Medical College, Jaipur, India. 3D-printed models were prepared for cranioplasty in 30 cases, CV junction anomalies in 18 cases, and brain tumors in 7 cases. Preoperative and postoperative data were analyzed as per the diagnosis.

Results:

In cranioplasty, cranial contour and approximation of the margins were excellent and esthetic appearance improved in all patients. In CV junction anomalies, neck pain and myelopathy were improved in all patients, as analyzed using the visual analog scale and the Japanese Orthopedic Association Scale score, respectively. Our questionnaire survey revealed that 3D models for brain tumors were useful in understanding space interval and depth intraoperatively with added advantage of patient education.

Conclusion:

Rapid prototyping 3D-printing technologies provide a practical and anatomically accurate means to produce patient-specific and disease-specific models. These models allow for surgical planning, training, simulation, and devices for the assessment and treatment of neurosurgical disease. Expansion of this technology in neurosurgery will serve practitioners, trainees, and patients.

Craniovertebral junction chordomas: Case series and strategies to overcome the surgical challenge

Introduction:

Chordomas are rare and malignant primary bone tumors. Different strategies have been proposed for chordomas involving the craniovertebral junction (CVJ) compared to other locations. The impossibility to achieve en bloc excision, the impact on stability and the need for proper reconstruction make their surgical management challenging.

Objective:

The objective is to discuss surgical strategies in CVJ chordomas operated in a single-center during a 7 years' experience (2013-2019).

Methods:

Adult patients with CVJ chordoma were retrospectively analyzed. The clinical, radiological, pathological, and surgical data were discussed.

Results:

A total number of 8 patients was included (among a total number of 32 patients suffering from skull base chordoma). Seven patients underwent endoscopic endonasal approach (EEA), and posterior instrumentation was needed in three cases. Three explicative cases were reported: EEA for midline tumor involving lower clivus and upper cervical spine (case 1), EEA and complemental posterior approach for occurred occipitocervical instability (case 2), C2 chordoma which required aggressive bone removal and consequent implant positioning, focusing on surgical planning (timing and type of surgical stages, materials and customization of fixation system) (case 3).

Conclusion:

EEA could represent a safe route to avoid injuries to neurovascular structure in clival locations, while a combined approach could be considered when tumor spreads laterally. Tumor involvement or surgical procedures could give raise to CVJ instability with the need of complementary posterior instrumentation. Thus, a tailored preoperative planning should play a key role, especially when aggressive bone removal and implant positioning are needed.

Case Report: A Case Series Using Natural Anatomical Gaps-Posterior Cervical Approach to Skull Base and Upper Craniocervical Meningiomas Without Bone Removal

Background: Removal of anteriorly located tumors of the upper cervical spine and craniovertebral junction (CVJ) is a particular surgical challenge. Extensive approaches are associated with pain, restricted mobility of neck and head and, in case of foramen magnum and clivus tumors, with retraction of brainstem and cerebellum.

Methods: Four symptomatic patients underwent resection of anteriorly located upper cervical and lower clivus meningiomas without laminotomy or craniotomy using a minimally invasive posterior approach. Distances of natural gaps between C0/C1, C1/C2, and C2/C3 were measured using preoperative CT scans and intraoperative lateral x-rays.

Results: In all patients, safe and complete resection was conducted by the opening of the dura between C0/C1, C1/C2, and C2/C3, respectively. There were no surgical complications. Local pain was reported as very moderate by all patients and postoperative recovery was extremely fast. All tumors had a rather soft consistency, allowing mass reduction prior to removal of the tumor capsule and were well separable from lower cranial nerves and vascular structures.

Conclusion: If tumor consistency is appropriate for careful mass reduction before removal of the tumor capsule and if tumor margins are not firmly attached to crucial structures, then upper cervical, foramen magnum, and lower clivus meningiomas can be safely and completely removed through natural gaps in the CVJ region. Both prerequisites usually become clear early during surgery. Thus, this tumor entity may be planned using this minimally invasive approach and may be extended if tumor consistency turns out to be less unfavorable for resection or if crucial structures cannot be easily separated from the tumor.

Historical insights, current and future perspectives in the neurosurgical and otorhinolaryngological alliance

Historically considered as a nobody’s land, craniovertebral junction (CVJ) surgery or specialty recently gained high consideration as symbol of challenging surgery as well as selective top level qualifying surgery. The alliance between Neurosurgeons and Otorhinolaringologists has become stronger in the time. CVJ has unique anatomical bone and neurovascular structures architecture. It not only separates from the subaxial cervical spine but it also provides a special cranial flexion, extension, and axial rotation pattern. Stability is provided by a complex combination of osseous and ligamentous supports which allows a large degree of motion. The perfect knowledge of CVJ anatomy and physiology allows to better understand surgical procedures of the occiput, atlas and axis and the specific diseases that affect the region. Although many years passed since the beginning of this pioneering surgery, managing lesions situated in the anterior aspect of the CVJ still remains a challenging neurosurgical problem. Many studies are available in the literature so far aiming to examine the microsurgical anatomy of both the anterior and posterior extradural and intradural aspects of the CVJ as well as the differences in all the possible surgical exposures obtained by 360° approach philosophy. Herein we provide a short but quite complete at glance tour across the personal experience and publications and the more recent literature available in order to highlight where this alliance between Neurosurgeon and Otorhinolaringologist is mandatory, strongly advisable or unnecessary.

Endoscopic-Assisted C2 Transverse Process Mass Excision

Background and Introduction

C2 transverse process exostoses are rare lesions. Due to critical structures surrounding them, their excision is challenging. There are sparse reports of anterior retropharyngeal approach (ARPA) for high-cervical transverse process mass and none for endoscopic ARPA approach.

Objective

A step-by-step technical report with its video is presented.

Surgical Technique

A 14-year-old girl presented with chronic right-sided neck pain. The computed tomography scan revealed a 6.5 cm³ mass in the right transverse process extending into the lateral mass of the C2 vertebra. The mass was anterior and in direct contact with the vertebral artery. She underwent a minimally invasive endoscopic ARPA.

Results

The mass could be excised along with its cartilaginous cap without any complications. The patient's symptoms resolved completely. The biopsy came out as osteochondroma.

Conclusion

Endoscopic ARPA is a minimally invasive option for high-cervical tumors and was found safe and effective for C2 transverse process osteochondroma.

Pathogenesis and Classification of Chiari Malformation Type I Based on the Mechanism of Ptosis of the Brain Stem and Cerebellum: A Morphometric Study of the Posterior Cranial Fossa and Craniovertebral Junction

Introduction  We investigated the mechanism of ptosis of the brain stem and cerebellum (hindbrain) in Chiari malformation type I (CM-I) and classified CM-I according to pathogenesis, based on a morphometric study of the posterior cranial fossa (PCF) and craniovertebral junction (CVJ). We discuss the appropriate surgical treatment for hindbrain ptosis. Materials and Methods  We examined 500 patients with CM-I and 100 healthy control individuals. We calculated the volume of the PCF (VPCF) and measured the axial length of the enchondral parts of the occipital bone and hindbrain. As statistical analyses, for the multiple analyses, heavy palindromic tests were used. Using three independent objective parameters, we tried to classify CM-I. Results  Three independent subtypes were confirmed (CM-I types A, B, and C). CM-I type A (167 cases): normal VPCF, normal volume of the area surrounding the foramen magnum (VSFM), and normal occipital bone size; CM-I type B (178 cases): normal VPCF, small VSFM, and small occipital bone size; and CM-I type C (155 cases): small VPCF, small VSFM, and small occipital bone size. Conclusions  Morphometric analyses of PCF and CVJ were very useful for the investigation of the mechanism of hindbrain ptosis and classifying CM-I according to pathogenesis. CM-I type A included mechanisms other than hindbrain ptosis, for example, CVJ instability, tethered cord, and increased intracranial pressure. CM-I types B and C demonstrated underdevelopment of the occipital bone. For CM-I types B and C, posterior decompression should be performed. For CM-I type A, appropriate surgical management should be selected.

C3 segmental vertebral artery and its surgical implication in craniovertebral junction anomalies: Insights from two cases

A spectrum of vertebral artery (VA) anomalies have been described with or without an associated congenital craniovertebral junction (CVJ) anomalies. C3 segmental VA, where the VA enters the dura at the level of C2/3 intervertebral foramen is an extremely rare anomaly. We report two cases of congenital CVJ anomaly (irreducible in one with C2/3 fusion and reducible in the other; without any subaxial fusion but with articular agenesis at C2/3 joint on the anomalous artery side). Computed tomographic angiography revealed intraspinal intradural entry of VA through the C2/3 intervertebral foramen on the right side with the contralateral artery found crossing the atlanto-axial joint. Both the patients underwent posterior approach and C2 was spared from instrumentation in both cases. Postoperatively, the patient with irreducible dislocation recovered well while the patient with reducible dislocation expired, possibly secondary to the thrombosis of the dominant VA from C2/3 foraminal encroachment. C3 segmental VA may be advantageous in aggressively exposing the C1/2 joint but instrumentation of C2 or C3 needs caution in view of the possibility of VA injury. Our experience shows that VA may be endangered even while exposing and protecting the artery. For such cases, we recommend posterior decompression of the C2/3 neural foramen during instrumentation in the absence of associated C2/3 fusion, as an abnormal joint morphology of C2/3 indicates a C2/3 instability.

Surgical Management of Chiari Malformations: Preliminary Results of Surgery According to the Mechanisms of Ptosis of the Brain Stem and Cerebellum

Introduction  We classified Chiari malformation type I (CM-I) according to the mechanism of ptosis of the brain stem and cerebellum, based on a morphometric study of the posterior cranial fossa (PCF) and craniovertebral junction (CVJ). Surgery was performed to manage the mechanism of the hindbrain ptosis. Materials and Methods  We calculated the volume of the PCF (VPCF) and the area surrounding the foramen magnum (VSFM) and measured the axial length of the enchondral parts of the occipital bone (occipital bone size) and the hindbrain. According to these measures, we classified CM-I into type A (normal VPCF, normal VSFM, and normal occipital bone size), type B (normal VPCF, small VSFM, and small occipital bone size), and type C (small VPCF, small VSFM, and small occipital bone size). Foramen magnum decompression (FMD) (280 cases) was performed on CM-I types A and B. Expansive suboccipital cranioplasty (ESCP) was performed on CM-I type C. Posterior craniocervical fixation (CCF) was performed in cases with CVJ instability. Lysis of the adhesion and/or sectioning of the filum terminale were performed on cases with tethered cord syndrome. Results  Both ESCP and FMD had a high rate of improvement of neurological symptoms (87%) and recovery rate. There was only small number of complications. CCF had a high rate of improvement of neurological symptoms (88%) and joint stabilization. Conclusion  In the management of Chiari malformation, appropriate surgical methods that address ptosis of the hindbrain should be chosen. Each surgical approach resulted in a good improvement of neurological symptoms.

Resection of a Lower Clival Meningioma via Posterolateral Approach: Two-Dimensional Operative Video

Objectives  This study aimed to demonstrate resection of a craniovertebral junction (CVJ) meningioma via the posterolateral approach.

Design  The study is designed with a two-dimensional operative video.

Setting  This study is conducted at department of neurosurgery in a university hospital.

Participants  A 50-year-old woman who presented with lower cranial nerve findings due to a left-sided lower clival meningioma ( Fig. 1 ).

Main Outcome Measures  Microsurgical resection of the meningioma and preservation of the neurovascular structures.

Results  The patient was placed in park-bench position and a left-sided retrosigmoid suboccipital craniotomy, followed by C1 hemilaminectomy and unroofing the lip of the foramen magnum, was performed. The dural incision extended from the suboccipital region down to the posterior arch of C2 ( Fig. 2 ). The arachnoid overlying the tumor was incised, revealing the course of the cranial nerve (CN) XI on the dorsolateral aspect of the tumor. The left vertebral artery (VA) was encased by the tumor which was originating from the dura below the jugular foramen. The mass was resected in a piecemeal fashion eventually. At the end of the procedure, all relevant cranial nerves and adjacent vascular structures were intact. Postoperative magnetic resonance imaging (MRI) confirmed total resection and the patient was discharged home on postoperative day 3 safely.

Conclusions  Microsurgical resection of the lesions of the CVJ are challenging as this transition zone between the cranium and upper cervical spine has a complex anatomy. Since adequate exposure of the extradural and intradural segments of the VA can be obtained by the posterolateral approach, this approach can be preferred in cases with tumors anterior to the VA or when the artery is encased by the tumor.

The link to the video can be found at: https://youtu.be/d3u5Qrc-zlM .

A morphological analysis of the cervical spine of the dolphin

Objective

Morphology of bones of cervical vertebrae of dolphin was studied. When compared to human vertebrae the structural modifications in terms of functional needs are evaluated.

Material

Morphological analysis of duly prepared bones of species D. delphis was carried out.

Result

The craniocervical junction and cervical spine of the dolphin (Delphinus delphis) has unique adaptations to allow for dorsoventrally undulating swimming movements as well as leaping out of water. The key differences from the human cervical spine include the absence of an odontoid process limiting rotatory movements, disproportionately short and wide vertebral bodies and a unilaterally elongated transverse process of the axis. Moreover, the cervical spine of the dolphin is disproportionally short compared to humans. These modifications give strength and stability to the cervical spine allowing maximal agility for flexion-extension movements of the lumbocaudal spine, which are keys for propulsion. The unilaterally elongated transverse process likely allows for rotatory spinning, suggesting possible lateral dominance of rotatory spin in this species.

Conclusions

Despite the skeletal adaptations, the cervical spine is strongly resonant of a mammalian heritage with a remarkably similar form and structure to house neurovascular contents and to allow muscular attachments.

The rhinopharyngeal flap for reconstruction of lower clival and craniovertebral junction defects

OBJECTIVE

The endoscopic endonasal approach (EEA) to the lower clivus and craniovertebral junction (CVJ) has been traditionally performed via resection of the nasopharyngeal soft tissues. Alternatively, an inferiorly based rhinopharyngeal (RP) flap (RPF) can be dissected to help reconstruct the postoperative defect and separate it from the oropharynx. To date, there is no evidence regarding the viability and potential clinical impact of the RPF. The aim of this study was to assess RPF viability and its impact on clinical outcome.

METHODS

A retrospective cohort of 60 patients who underwent EEA to the lower clivus and CVJ was studied. The RPF was used in 30 patients (RPF group), and the nasopharyngeal soft tissues were resected in 30 patients (control group).

RESULTS

Chordoma was the most common surgical indication in both groups (47% in the RPF group vs 63% in the control group, p = 0.313), followed by odontoid pannus (20% in the RPF group vs 10%, p = 0.313). The two groups did not significantly differ in terms of extent of tumor (p = 0.271), intraoperative CSF leak (p = 0.438), and skull base reconstruction techniques other than the RPF (nasoseptal flap, p = 0.301; fascia lata, p = 0.791; inlay graft, p = 0.793; and prophylactic lumbar drain, p = 0.781). Postoperative soft-tissue enhancement covering the lower clivus and CVJ observed on MRI was significantly higher in the RPF group (100% vs 26%, p < 0.001). The RPF group had a significantly lower rate of nasoseptal flap necrosis (3% vs 20%, p = 0.044) and surgical site infection (3% vs 27%, p = 0.026) while having similar rates of postoperative CSF leakage (17% in the RPF group vs 20%, p = 0.739) and meningitis (7% in the RPF group vs 17%, p = 0.424). Oropharyngeal bacterial flora dominated the infections in the control group but not those in the RPF group, suggesting that the RPF acted as a barrier between the nasopharynx and oropharynx.

CONCLUSIONS

The RPF provides viable vascularized tissue coverage to the lower clivus and CVJ. Its use was associated with decreased rates of nasoseptal flap necrosis and local infection, likely due to separation from the oropharynx.

[Treatment of syringomyelia in patients with arachnopathy within craniovertebral junction]

One of the causes of syringomyelia is arachnopathy following an infectious or non-infectious inflammation of the arachnoid membrane. It is extremely rare that adhesive arachnoiditis develops within the occipital cistern and impairs cerebrospinal fluid flow from the foramen of Magendie, along posterior cerebellar surface and into spinal subarachnoid space. These process result syringomyelia.

OBJECTIVE

To evaluate postoperative outcomes in patients with syringomyelia following arachnopathy at the craniovertebral level.

MATERIAL AND METHODS

A retrospective analysis included 27 patients with syringomyelia and arachnopathy within the occipital cistern for the period from 2013 to 2018. Eight patients (29.6%) underwent primary surgery. In this group, 2 patients had arachnopathy following post-traumatic subarachnoid hemorrhage, 1 - after non-traumatic subarachnoid hemorrhage in posterior cranial fossa, 2 - after bacterial meningitis, 3 - the cause was unclear. Nineteenth patients underwent redo surgery after previous procedures on posterior cranial fossa (tumor resection - 3 patients, suboccipital decompression for Chiari malformation - 16 cases). High-resolution MRI with special protocols for analysis of CSF circulation and mobility of brain structures was used to diagnose arachnopathy (phase contrast ECG-synchronized MRI, TrueFISP).

RESULTS

Surgeries were aimed at mobilization of cerebellar tonsils and spinal cord and restoration of CSF circulation at the craniovertebral level. One year later, 13 (48.1%) patients noted improvement in their condition, 8 (29.6%) patients - clinical stabilization. In most cases, stabilization or improvement of sensory and coordination disorders. Syringomyelia symptoms progressed in 6 (22.2%) patients. Mean preoperative mJOA score was 11.86±1.24, in a year after surgery - 14.17±1.19. According to MRI data after 1 year, syringomyelia disappeared in 2 patients (7.4%), reduced in 13 (48.1%) cases, remained the same in 9 (33.3%) cases and deteriorated in 3 (11.1%) patients. Vaquero index reduced from 45.5% to 21.6 within a year after surgery. Early postoperative complications occurred in 3 (11.1%) patients: 1 (3.7%) had hydrocephalus and 2 (7.4%) had aseptic meningitis.

CONCLUSION

Modern diagnostic and surgical methods for syringomyelia ensure favorable outcomes in 77.7% of cases.

Intraoperative surveillance of the vertebral artery using indocyanine green angiography and Doppler sonography in craniovertebral junction surgeries

OBJECTIVE

The authors sought to evaluate the usefulness of indocyanine green (ICG) angiography and Doppler sonography for monitoring the vertebral artery (VA) during craniovertebral junction (CVJ) surgery and compare the incidence of VA injury (VAI) between the groups with and without the monitoring of VA using ICG angiography and Doppler sonography.

METHODS

In total, 344 consecutive patients enrolled who underwent CVJ surgery. Surgery was performed without intraoperative VA monitoring tools in 262 cases (control group) and with VA monitoring tools in 82 cases (monitoring group). The authors compared the incidence of VAI between groups. The procedure times of ICG angiography, change of VA flow velocity measured by Doppler sonography, and complication were investigated.

RESULTS

There were 4 VAI cases in the control group, and the incidence of VAI was 1.5%. Meanwhile, there were no VAI cases in the monitoring group. The procedure time of ICG angiography was less than 5 minutes (mean [± SD] 4.6 ± 2.1 minutes) and VA flow velocity was 11.2 ± 4.5 cm/sec. There were several cases in which the surgical method had to be changed depending on the VA monitoring. The combined use of ICG angiography and Doppler sonography was useful not only to monitor VA patency but also to assess the quality of blood flow during CVJ surgery, especially in the high-risk group of patients.

CONCLUSIONS

The combined use of ICG angiography and Doppler sonography enables real-time intraoperative monitoring of the VA by detecting blood flow and flow velocity. As the arteries get closer, they provide auditory and visual feedback to the surgeon. This real-time image guidance could be a useful tool, especially for high-risk patients and inexperienced surgeons, to avoid iatrogenic VAI during any CVJ surgery.

Endoscopic Endonasal Transclival Odontoidectomy for Basilar Invagination: Operative Video and Technical Nuances

Basilar invagination is a congenital or acquired craniovertebral junction abnormality where the tip of the odontoid process projects through the foramen magnum which can cause severe symptomatic compression of the brainstem and spinal cord. If left untreated, patients can develop progressive quadriparesis. Traditionally, basilar invagination can be treated with cervical traction and posterior stabilization. However, in irreducible cases, anterior decompression via a transoral or endonasal approach may be necessary. In this operative video, we demonstrate an endoscopic endonasal transclival approach for odontoidectomy to successfully treat a 37-year-old female with severe basilar invagination causing symptomatic compression on the cervicomedullary junction resulting in unsteady gait and motor weakness. The patient had Klippel–Feil syndrome where the C1 arch was assimilated to the foramen magnum and transclival drilling was needed to adequately access the odontoid process for removal. A second-stage posterior occipitocervical stabilization and fusion was performed the following day. Immediate postoperative imaging showed excellent decompression of the cervicomedullary junction. Postoperatively, the patient had significant improvement in gait and motor strength in all extremities, and was ambulating independently without assistance at 1 year after surgery. The endoscopic endonasal transclival odontoidectomy is a useful strategy to treat severe irreducible basilar invagination causing symptomatic neural compression. The surgical technique and nuances are described in a step-by-step fashion in this illustrative operative video.

The link to the video can be found at: https://youtu.be/HL4K7KqJEJM.

A novel classification and algorithmic-based management of craniovertebral junction osteoarthrosis

Introduction:

The objective of this study is to propose a novel classification and algorithmic-based management plan for craniovertebral junction osteoarthrosis (CVJOA).

Materials and Methods:

A retrospective study was done based on prospective database of radiological studies and clinical history. Twenty symptomatic patients (12 females and 8 males) with a mean age of 54.8 years were identified with CVJOA. These patients underwent either nonsurgical treatment only or surgical intervention and had follow-up of at least 14 months. Classification of CVJOA is based on coronal deformity, rigidity, stability, and two modifiers. The main surgical procedures done in the surgical arm of these patients included C1–C2 fusion, C1–C2 facet distraction and fusion, and unilateral subaxial facet distraction, and posterior column osteotomy.

Results:

All the twenty patients included in this study complained of either sub-occipital or upper neck pain and had radiological evidence of CVJOA. Seven patients improved with nonsurgical management and 13 underwent surgical intervention. Surgical recommendations for each type of CVJOA have been described with case examples, and algorithm for the management of CVJOA has been developed based on this study. Interobserver agreement on CVJOA classification was measured using kappa value statistics which showed moderate strength of agreement (0.467).

Conclusion:

This study describes a novel classification and management of CVJOA based on algorithm and current surgical recommendations for each type of CVJOA.

Endoscopic Transnasal Odontoidectomy

Background  Odontoidectomy may represent the treatment of choice for symptomatic ventral craniovertebral junction stenosis in selected cases. An endoscopic transnasal approach has been proposed as an alternative to a classic transoral approach. Method  We report a case of a patient with a craniovertebral junction stenosis due to the ossification of the posterior ligament. The clinical and radiological records of the patient and a step-by-step description of the surgical technique are presented ( Fig. 1 ). Conclusion  Endoscopic transnasal odontoidectomy provides a direct access to the dens and adjacent structures of the anterior upper cervical spine with a less invasive burden on the oropharingeal structures. The link to the video can be found at: https://youtu.be/Ofrk1sFTV9I .

Isolated Hypoglossal Nerve Palsy Due to an Osteophyte with Atlantoaxial Dislocation

Isolated hypoglossal nerve palsy (IHP), or hypoglossal nerve palsy without any other neurological signs, is rare. We report a woman with atlantoaxial dislocation (AAD) who presented with IHP due to hypoglossal nerve compression by an osteophyte at the hypoglossal canal. A 77-year-old woman presented with speech difficulties and the feeling of a swollen tongue on the left side for 3 days. Her only neurological feature was left hypoglossal nerve palsy. She had been diagnosed with AAD 2 years before. Computed tomography (CT) and high-resolution magnetic resonance imaging (MRI) revealed the compression of the basicranial hypoglossal nerve at the external orifice of the hypoglossal canal by an AAD osteophyte which was causing IHP. IHP can develop due to hypoglossal nerve compression by an osteophyte from AAD. CT and high-resolution MRI revealed this rare mechanism of IHP.

Expanding the phenotype of Wiedemann-Steiner syndrome: Craniovertebral junction anomalies

Wiedemann-Steiner syndrome (WDSTS) is a rare autosomal dominant condition caused by heterozygous loss of function variants in the KMT2A (MLL) gene, encoding a lysine N-methyltransferase that mediates a histone methylation pattern specific for epigenetic transcriptional activation. WDSTS is characterized by a distinctive facial phenotype, hypertrichosis, short stature, developmental delay, intellectual disability, congenital malformations, and skeletal anomalies. Recently, a few patients have been reported having abnormal skeletal development of the cervical spine. Here we describe 11 such individuals, all with KMT2A de novo loss-of-function variants: 10 showed craniovertebral junction anomalies, while an 11th patient had a cervical abnormality in C7. By evaluating clinical and diagnostic imaging data we characterized these anomalies, which consist primarily of fused cervical vertebrae, C1 and C2 abnormalities, small foramen magnum and Chiari malformation type I. Craniovertebral anomalies in WDSTS patients have been largely disregarded so far, but the increasing number of reports suggests that they may be an intrinsic feature of this syndrome. Specific investigation strategies should be considered for early identification and prevention of craniovertebral junction complications in WDSTS patients.

Occipital condyle syndrome in a case of rotatory atlantoaxial subluxation (type II) with craniovertebral junction tuberculosis: Should we operate on "active tuberculosis?"

Tuberculosis of the craniovertebral junction is rare as well as intriguing. We present a unique amalgamation of three rare entities: craniovertebral tuberculosis, occipital condyle syndrome, and nontraumatic type II rotatory atlantoaxial dislocation in one patient. We reviewed the limited literature available and the underlying pathophysiology to highlight the pattern of the disease presentation, progression, and response to management options. A 13-year-old girl presented with neck pain, torticollis, and right hypoglossal weakness following a fall from stairs 10 months back. Radiological investigation suggested right occipital condylar destruction with right-sided neck tilt and rotatory atlantoaxial dislocation. The contrast magnetic resonance imaging was suggestive of craniovertebral tuberculosis with primary foci in the right lung (apical cavitary lesion). In view of an intact neurological condition, she was started on antitubercular treatment and she continues to do well during the follow-up. It remains debatable if an anticipation of this problem calls for a surgical addressal at the acute stage of the disease as a delayed correction is likely to be more complex. While a halo device is preferable in these cases, it remains cumbersome and less preferred in comparison to the Philadelphia collar.

[Anatomy of anterior craniovertebral junction in endoscopic transnasal approach]

Modern achievements in endoscopic technologies ensure extending the indications for endoscopic transnasal approach in skull base surgery. Knowledge on topographic anatomy of craniovertebral junction is a prerequisite for surgical interventions in this area. Transnasal endoscopic surgery of craniovertebral junction is a relatively new field. Therefore, this manuscript and similar anatomical studies are extremely important for neurosurgeons.

Perimedullary arteriovenous fistulas of the craniovertebral junction: A systematic review

Perimedullary arteriovenous fistulas (PMAVFs) are uncommon vascular malformations, and they rarely occur at the level of the craniovertebral junction (CVJ). The therapeutic management is challenging and can include observation alone, endovascular occlusion, or surgical exclusion, depending on both patient and malformation characteristics. A systematic literature search was conducted using MEDLINE, Scopus, and Google Scholar databases, searching for the following combined MeSH terms: (perimedullary arteriovenous fistula OR dural arteriovenous shunt) AND (craniocervical junction OR craniovertebral junction). We also present an emblematic case of PMAVF at the level of the craniovertebral junction associated to a venous pseudoaneurysm. A total of 31 published studies were identified; 10 were rejected from our review because they did not match our inclusion criteria. Our case was not included in the systematic review. We selected 21 studies for this systematic review with a total of 58 patients, including 20 females (34.5%) and 38 males (65.5%), with a female/male ratio of 1:1.9. Thirty-nine out of 58 patients underwent surgical treatment (67.2%), 15 out of 58 patients were treated with endovascular approach (25.8%), 3 out of 58 patients underwent combined treatment (5.2%), and only 1 patient was managed conservatively (1.7%). An improved outcome was reported in 94.8% of cases (55 out of 58 patients), whereas 3 out of 58 patients (5.2%) were moderately disabled after surgery and endovascular treatment. In literature, hemorrhagic presentation is reported as the most common onset (subarachnoid hemorrhage in 63% and intramedullary hemorrhage in 10%), frequently caused either by venous dilation, due to an ascending drainage pathway into an intracranial vein, or by the higher venous flow rates that can be associated with intracranial drainage. Hiramatsu and Sato stated that arterial feeders from the anterior spinal artery (ASA) and aneurysmal dilations are associated with hemorrhagic presentation. In agreement with the classification by Hiramatsu, we defined the PMAVF of the CVJ as a vascular lesion fed by the radiculomeningeal arteries from the vertebral artery and the spinal pial arteries from the ASA and/or lateral spinal artery. Considering the anatomical characteristics, we referred to our patient as affected by PMAVF, even if it was difficult to precisely localize the arteriovenous shunts because of the complex angioarchitecture of the fine feeding arteries and draining veins, but we presumed that the shunt was located in the point of major difference in vessel size between the feeding arteries and draining veins. PMAVFs of CVJ are rare pathologies of challenging management. The best diagnostic workup and treatment are still controversial: more studies are needed to compare different therapeutic strategies concerning both long-term occlusion rates and outcomes.

Management of Atlantoaxial Instability Due to a Pathological Fracture of the Axis

Metastases to the upper cervical spine are uncommon, and subsequent instability is rare. We report the details of a patient with metastatic breast cancer to the axis manifesting as a pathologic fracture and C1/C2 instability. This was treated by preoperative reduction to appropriate alignment with use of crown halo traction, followed by posterior occipitocervical fusion and postoperative radiation therapy. 

Microanatomy of the dura mater at the craniovertebral junction and spinal region for safe and effective surgical treatment

OBJECTIVE

Few reports have been published regarding the detailed microsurgical anatomy of the dura mater at the craniovertebral junction (CVJ), although many neurosurgeons have had the opportunity to conduct surgeries in this region, such as in cases of Chiari malformation. The authors aimed to evaluate the detailed and precise microsurgical anatomy of the dura mater at the CVJ for safe and effective surgical treatment at this area.

METHODS

This study consisted of dissection of 4 formalin-fixed, continuous, human cadaveric dura maters, extending from the posterior fossa to the C2 level. After removing the occipital bone and C1 laminae, a dural incision was made to harvest the specimen. The following structural and topographical aspects of the dura mater in each region were studied: 1) thickness, 2) morphological characteristics, and 3) vascular structures.

RESULTS

The average thicknesses of the dura mater were 313.4 ± 137.0 μm, 3051.5 ± 798.8 μm, and 866.5 ± 359.0 μm in the posterior cranial fossa, CVJ, and spinal region, respectively. The outer layer of the posterior cranial dura mater and the tendon of the rectus capitis posterior minor muscle were connected, forming the "myodural bridge." The dura mater at the CVJ had a well-developed vascular network. These vascular structures were determined to be veins or the venous sinus, and were mainly located around the interface between the inner layer of the cranial dura mater and the rectus capitis posterior minor muscle layer. Regarding the morphological features, the bulging located in the inner layer of the dura mater at the CVJ was determined to be the marginal sinus, and contained a pacchionian granulation that allowed for CSF circulation. In the spinal region, the dura mater was characterized by a single, thick layer enclosing the collagen fibers with almost the same orientation.

CONCLUSIONS

The dura mater at the CVJ displayed dynamic morphological changes within an extremely short segment. Its characteristic anatomical features were not similar to those in the cranial regions. The dural bulging at the CVJ was determined to be the venous sinus. During surgery in the posterior fossa, CVJ, and spinal cord, different procedures should be used because of the specific microsurgical anatomy of each region.

Extirpation of a Ruptured Anterior Spinal Artery Aneurysm Accompanied by Dural Arteriovenous Fistula at the Craniovertebral Junction via a Posterolateral Approach: The Management of Extradural Venous Congestion

Objective  This study was aimed to discuss how to control extradural venous congestion with an increased pressure in cases of arteriovenous shunt disease of the craniovertebral junction.

Design  The study is presented through an operative video.

Results  A 77-year-old patient with subarachnoid hemorrhage had a dural arteriovenous fistula located at the C1–C2 level. Left vertebral angiography showed a fistula between the left C2 radiculomeningeal muscular artery and perivertebral plexus. Furthermore, right vertebral angiography showed a ruptured aneurysm at the aberrant branch of the anterior spinal artery originating from the contralateral vertebral artery (VA), possibly formed because of the concurrently increased pressure of the perimedullary veins. Aneurysm extirpation was planned through a posterolateral approach. To reduce venous bleeding during the approach, preoperative embolization of the radiculomeningeal muscular artery was performed. During surgery, the suboccipital triangle was exposed following layer-by-layer dissection of the suboccipital muscles ( Figs. 1 and 2 ). Subperiosteal dissection of the paravertebral plexus surrounding the VA around the C1 lamina was effective to avoid venous bleeding. A bloodless operative field was achieved, and key anatomical structures, such as the C2 nerve root, feeder, and V3 portion of the left VA, were clearly identified. With a sufficient amount of lateral exposure, the ruptured anterior spinal artery aneurysm was successfully extirpated with bipolar coagulation. The patient was discharged with no neurologic deficit.

Conclusion  Controlling extradural venous congestion is essential to obtain a clear operative field in cases of arteriovenous shunt disease at the craniovertebral junction.

The link to the video can be found at: https://youtu.be/fCT69WtAQbo .

Left Far Lateral Craniotomy for Clipping of a Posterior Inferior Cerebellar Artery Aneurysm

Objectives  The complex anatomical relationships of neurovascular structures at the craniovertebral junction make the clipping of a posterior inferior cerebellar artery (PICA) aneurysm surgically challenging. We demonstrate the clipping of a PICA aneurysm in the video.

Design, Setting, and Participant  A 65-year-old woman presented with a nonsymptomatic unruptured left PICA aneurysm; follow-up angiography showed an increase in its size. Preoperative angiography demonstrated a PICA aneurysm with the neck close to the origin of the PICA. A daughter sac of the aneurysm was also noted. A left far lateral approach was performed. The vagoaccessory triangle was exposed after opening the arachnoid membrane. The origin of the PICA and the aneurysm were revealed after exploration. The aneurysm neck was identified both proximally and distally. Two fenestrated clips were applied; subsequent indocyanine green (ICG) videoangiography demonstrated that the PICA was obstructed. One clip was adjusted, and repeated ICG videoangiography showed the PICA was patent. An endoscope was used before and after the clip application to better understand the anatomy of the aneurysm and inspect clip positions ( Fig. 1 ).

Outcome  The patient was neurologically intact postoperatively and was discharged on postoperative day 4.

Conclusion  PICA aneurysms require careful treatment. Impingement of adjacent structures can cause severe complications. Lower cranial nerve damage can cause dysphagia, and compromised vertebral/PICA circulation can cause brainstem symptoms, such as Wallenberg's syndrome. Intraoperative ICG videoangiography should be used to evaluate vessel patency, and the endoscope should be used to fully inspect the aneurysm and evaluate the clip application.

The link to the video can be found at: https://youtu.be/dKxFQTRA89g .

Anterolateral Approach with Endoscopic Assistance for Resection of a Craniovertebral Junction Chordoma

Craniovertebral junction chordomas can represent a surgical challenge, especially when intradural extension and contact with neurovascular structures is involved. To date, there is still controversy on the choice of optimal surgical corridor for such lesions, with endoscopic endonasal, far lateral and anterolateral corridors being those most commonly used. In this operative video, we present a case of craniovertebral junction chordoma with significant bone destruction and intradural extension ( Fig. 1 ). The tumor was safely removed using an anterolateral approach with transposition of the vertebral artery to gain access to the lateral craniovertebral junction. The endoscope is demonstrated to help with intradural tumor removal, providing a wide angle of view through a relatively narrow dural opening ( Fig. 2 ). In this video, nuances of the anterolateral approach, chordoma removal strategies and closure technique are presented in detail. A gross total resection was achieved, and the postoperative course was uneventful. In summary, the anterolateral approach with endoscopic assistance can offer a safe and effective corridor for the surgical management of craniovertebral junction chordomas.

The link to the video can be found at: https://youtu.be/pC0YxKgNoMY .

Endoscopic Endonasal Odontoidectomy

Odontoidectomy is a standard procedure employed in the treatment of irreducible, compressive ventral pathologies of the craniovertebral junction (CVJ). The traditionally used transoral route is often challenging due to the increased depth of the surgical corridor and risk of injuries to the soft tissues in the oral cavity. The emergence of endoscopic endonasal (EE) surgery has provided an attractive alternative route to the traditional treatment algorithm, and it has the advantages of avoiding complications related to tongue swelling, tracheal swelling, prolonged intubation, velopharyngeal insufficiency, dysphagia, and dysphonia.

We present a case of a 66-year-old man with no pertinent past medical history, who presented with progressive quadriparesis and gait ataxia over last 6 months (Nurick's grade 2). Neurological exam revealed pattern suggestive of high-cervical myelopathy with no evidence of cranial nerve paresis. Magnetic resonance imaging (MRI) of his CVJ revealed a large pannus behind the dens with severe spinal cord compression, mild contrast enhancement was noted posterior to the pannus, likely from the ligamentous structures; pannus was hypointense on both T1- and T2-weighted images. Further, a computerized tomography (CT) scan did not reveal any obvious malalignment. He underwent an EE odontoidectomy, followed by posterior cervical fusion. He had an unremarkable postoperative period and recovered fully from his myelopathy over the next 6 months. The histopathological examination of the pannus revealed a degenerated disk. In this video, we have a step by step description of the EE approach to the odontoid and discuss the surgical nuances.

The link to the video can be found at: https://youtu.be/pjg68_vK0C4 .